A head mounted display device (a head mounted display; HMD), which is a display device mounted on the head, is known. For example, the head mounted display device generates, using a liquid crystal display and a light source, image light representing an image and guides the generated image light to the eyes of a user using a projection optical system and a light guide plate to thereby cause the user to visually recognize a virtual image. As the head mounted display device, there are two types: a transmission type for enabling the user to visually recognize an outside scene in addition to the virtual image and a non-transmission type for disabling the user to visually recognize the outside scene. As the head mounted display device of the transmission type, there are an optical transmission type and a video transmission type.
PTL 1 discloses a technique for analyzing a tilt of the head of a user of a head mounted display device to calculate a tilt of the head mounted display device with respect to the horizontal plane, analyzing a movement of a predetermined part (e.g., an arm) of the user to calculate a movement amount of the user in a predetermined time, and, when the movement amount is equal to or larger than a predetermined value, gradually tilting a video in a continuous plurality of frames to correct the tilt of the head mounted display device and suppress visually induced motion sickness caused by a shift between an outside scene and the video visually recognized by the user. PTL 2 discloses a technique for causing, in a region of a video that a head mounted display device causes a user to visually recognize, a peripheral section of the video, which considerably affects visually induced motion sickness, to emit light to suppress the visually induced motion sickness of the user.